code: def test_answer_only_loss(self):
      tokenizer = get_nmt_tokenizer(
          library="sentencepiece", tokenizer_model=TOKENIZER_FILE_Llama2
      )
      self._packed_seq_test(tokenizer, answer_only_loss=True)
  
file_path: NeMo/tests/collections/nlp/test_packed_sft_dataset.py
imports: import os
  import numpy
  import pytest
  from nemo.collections.nlp.data.language_modeling.megatron.gpt_sft_dataset import GPTSFTPackedDataset
  from nemo.collections.nlp.modules.common.tokenizer_utils import get_nmt_tokenizer
label_desc: Use image node_id 3 for calling the TestGPTSFTPackedDataset obj's underlying member method code with example usage: obj.test_answer_only_loss() without return types